So the state says I have to mount a front licences plate on my car. I have a new mount bracket and was looking to bolt it on but I cant figure out what is holding my bumper on now. The pictures below show the bumper on the car looking up. As you can see the bumper mounting hardware are plastic and are holding the bumper on quite tight. I tried to pull one off but it isnt budging and I dont want to break it.

Anyone know what these are and how to take them off. What hardware should I have, hex bolts, philip bolts?

Here is the fastener I just pulled out of the bumper. No need to pull the other 4 after I get the Liscense bracket installed, they were installed quite securely. Dimension was 3/8" + wide and about 7/8" tall. (The line at the 4 is actually the 3/4" and 7/8" on the ruler)